Sump pipe flow rate question?

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wheatgerm

wheatgerm

Plecostomus
MFK Member
May 22, 2010
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This is going to be hard to explain without pictures but ill try...
I have an external evo 3500 pump, I've had it set up on a few other tanks but now I want to set it up on my 400 a little bit differently, in the past I've used 2 sumps and had them connected with 2 inch bulkheads with a T in the middle so my pump was pulling from both sumps equally and since the bulkheads were connecting the sumps together the water level stayed the same in both sumps.
On This set up I want my first sump to hold the filter socks then connect the first to the second sump with 2in pipe. The second will hold the bio and other filtration. Then the second will connect to the pump. The only difference from the first time I had it set up will be that the pump will only pull out of the second sump instead of being in the middle of the two... will the pipe connecting the sumps be able to keep up with the flow and keep the water levels equal or will I end up draining one sump?

Im thinking it wont make a difference because even when the pump was in the middle it only was connected by a single 2inch pipe T'd off so flow rates should be the same correct? Or am I wrong?

I hope you guys can picture this lol

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I'm assuming the pump is rated for 3500 gph? If so, and if I'm picturing this correctly, I would say it isn't going to work the way you want it to. With the pump off, the water height will be the same in both sumps. When you turn it on, sump 2 level will drop. The level difference will push the water from sump 1 into sump 2 through the 2" pipe. Water will then be returned to the tank from sump 2 only. This is the theory? If so, I don't think that the water pressure in sump 1 will be anywhere near enough to push the water into sump2 fast enough to keep up with a 3500 gph pump... Limiting factor being the 2" pipe. Depending on the size and water level of the sumps, you will either overflow sump 1 or suck sump 2 dry.


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2" pipe at full siphon will flow around 4,500+gph. You'll be fine with your plan, it will keep up.
 
frnchjeep said:
I'm assuming the pump is rated for 3500 gph? If so, and if I'm picturing this correctly, I would say it isn't going to work the way you want it to. With the pump off, the water height will be the same in both sumps. When you turn it on, sump 2 level will drop. The level difference will push the water from sump 1 into sump 2 through the 2" pipe. Water will then be returned to the tank from sump 2 only. This is the theory? If so, I don't think that the water pressure in sump 1 will be anywhere near enough to push the water into sump2 fast enough to keep up with a 3500 gph pump... Limiting factor being the 2" pipe. Depending on the size and water level of the sumps, you will either overflow sump 1 or suck sump 2 dry.


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Click to expand...

Sounds like your picturing it right, as sump 1 fills up it will have to equal out sump 2. The only thing I was to clarify is that the connection pipe between the sumps will be towards the bottom of the sumps. Also they are each 50 gallons.
This is a total guess, but after I neck down the return and after head height ect im assuming ill be around 2600-3000gph on the sump. I also have a ball valve I can throttle it back a little.

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rbarn said:
2" pipe at full siphon will flow around 4,500+gph. You'll be fine with your plan, it will keep up.
Click to expand...

If your number is correct then you simplified my question very quickly lol. I could have just asked how much gph can flow threw a 2" straight pipe if its not being pushed with a pump

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http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml

This link shows gravity fed max flow for 2 inch pipe being around 3300gph. I still don't know if ill trust the idea until I try it? But it seems possible from the numbers...
Any other input? Id like to think everything threw before I cut holes in the sumps

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Its not going to be "a full syphon" so the math is wrong just saying the 2" pipe flows *** at a full syphon.

Think about a large tank of water and you drill a hole on the very bottom then drill a hole half way up then drill at the top. Which hole will push out more water? Same goes with your sump. If the 2" hole is at the bottom and the water level is just above it then not much water is going to flow. As the water rises in the sump you will have more flow. My guess is your sump is not deep enough to get the flow required to keep up with the pump.
Yes a 2" pipe can do it.
No, it wont work in your application.
 
Egon said:
Its not going to be "a full syphon" so the math is wrong just saying the 2" pipe flows *** at a full syphon.

Think about a large tank of water and you drill a hole on the very bottom then drill a hole half way up then drill at the top. Which hole will push out more water? Same goes with your sump. If the 2" hole is at the bottom and the water level is just above it then not much water is going to flow. As the water rises in the sump you will have more flow. My guess is your sump is not deep enough to get the flow required to keep up with the pump.
Yes a 2" pipe can do it.
No, it wont work in your application.
Click to expand...

So would it work better to run a T between them then have the T feed the pump? This way has worked in the past and both sumps have equal water levels.

I guess I dont understand why it wont work if sump 1 is feeding sump 2 with a 2 inch pipe and sump 2 is feeding the pump with a 2 inch pipe why it wouldn't stay equalized?

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Well we have a 1.5 hp pool pump for are 500 gallon tank with sump. But all together it's 800 gallons. The pump is a 9600 gph and we have 5 1.5 inch bulkheads that gravity feed in to the sump. And we used all 1.5 inch pipe. But right after the bulkheads put a (T) in and about a 6" inch long peace of pipe pointing straight up to give it air to maximize the flow. Kinda a breathing tube.

And the ( T) idea on the two sumps might be the best bet for them to be equal. Because if not you would have to make the pipe between the two bigger so it can keep up with the pump. If that makes sense.

Well hope I helped a little and good luck


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